From 44fcd213f975ae35fb92de9bc56d8d895478edb5 Mon Sep 17 00:00:00 2001
From: Madison Lynch <madi@mxdi.xyz>
Date: Wed, 16 Apr 2025 16:18:33 -0700
Subject: [PATCH] Improved memory-safety in dyn_battery function

---
 Makefile                 |  1 +
 components/dyn_battery.c | 84 ++++++++++++++++++++++++++++++++++++++++
 config.def.h             |  3 ++
 slstatus.h               |  3 ++
 4 files changed, 91 insertions(+)
 create mode 100644 components/dyn_battery.c

diff --git a/Makefile b/Makefile
index 7a18274..d1b24dd 100644
--- a/Makefile
+++ b/Makefile
@@ -11,6 +11,7 @@ COM =\
 	components/cpu\
 	components/datetime\
 	components/disk\
+	components/dyn_battery\
 	components/entropy\
 	components/hostname\
 	components/ip\
diff --git a/components/dyn_battery.c b/components/dyn_battery.c
new file mode 100644
index 0000000..9377071
--- /dev/null
+++ b/components/dyn_battery.c
@@ -0,0 +1,84 @@
+/* Written by Madison Lynch <madi@mxdi.xyz> */
+/* Only Linux is supported */
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+#include <dirent.h>
+
+#include "../slstatus.h"
+
+#define BAT_PREFIX "BAT"
+#define BAT_DIR "/sys/class/power_supply"
+
+/**
+* Counts number of batteries detected by system.
+*
+* @return unsigned integer denoting the number of detected batteries.
+* @author Madison Lynch
+*/
+static unsigned int
+battery_count(void) {
+    DIR *dir = opendir(BAT_DIR);
+    unsigned int bat_c = 0;
+
+    struct dirent *entry;
+    while((entry = readdir(dir)))
+        if(strlen(entry->d_name) > 3)
+            if(strncmp(entry->d_name, BAT_PREFIX, 3) == 0)
+                bat_c++;
+
+    (void) closedir(dir);
+    return bat_c;
+}
+
+/**
+* Displays the status and capacity of a dynamic amount of batteries (i.e.
+* laptop may have secondary external battery).
+*
+* @param  fmt format string to use for each battery display. ordered key:
+*             %u: battery number || %s: battery state || %s battery capacity
+* @return string containing the status and capacities of all detected batteries
+* @author Madison Lynch
+*/
+const char *
+dyn_battery(const char *fmt) {
+    static char *ret;
+    free(ret); // Free address from previous output
+
+    const size_t fmt_s = strlen(fmt);
+    const unsigned int bat_c = battery_count();
+
+    // Extra byte in calloc() for null byte
+    ret = (char *)calloc(fmt_s * bat_c + 1, sizeof(char));
+    if(!ret) {
+        fprintf(stderr, "dyn_battery: calloc() failed.");
+        return NULL;
+    }
+
+    unsigned int displacement = 0; // For appending battery displays
+    for(unsigned int i=0; i<bat_c; i++) {
+        char bat[7]; // "BAT" = 3 + <=3 digit number + null byte
+        (void) sprintf(bat, "BAT%u", i);
+
+        // Add battery display to final string to be returned
+        (void) sprintf(
+            ret + displacement,
+            fmt,
+            i,
+            battery_state(bat),
+            battery_perc(bat)
+        );
+        displacement = strlen(ret);
+
+        // Add space between battery displays
+        ret[displacement++] = ' ';
+    }
+
+    // Remove extra space after last battery display
+    ret[--displacement] = '\0';
+
+    return ret;
+}
+
+#undef BAT_DIR
+#undef BAT_PREFIX
diff --git a/config.def.h b/config.def.h
index d805331..a0052e3 100644
--- a/config.def.h
+++ b/config.def.h
@@ -26,6 +26,9 @@ static const char unknown_str[] = "n/a";
  * disk_perc           disk usage in percent           mountpoint path (/)
  * disk_total          total disk space in GB          mountpoint path (/)
  * disk_used           used disk space in GB           mountpoint path (/)
+ * dyn_battery         displays the name, state and    format string (%u, %s,
+ *                     capacity of all detected        %s). order is important,
+ *                     batteries                       and matches description.
  * entropy             available entropy               NULL
  * gid                 GID of current user             NULL
  * hostname            hostname                        NULL
diff --git a/slstatus.h b/slstatus.h
index 8ef5874..44a4b61 100644
--- a/slstatus.h
+++ b/slstatus.h
@@ -21,6 +21,9 @@ const char *disk_perc(const char *path);
 const char *disk_total(const char *path);
 const char *disk_used(const char *path);
 
+/* dyn_battery */
+const char *dyn_battery(const char *fmt);
+
 /* entropy */
 const char *entropy(const char *unused);
 
-- 
2.49.0